Charcoal derived from incomplete combustion of vegetation is ubiquitous and potentially effective for sequestra tion of environmental contaminants.To demonstrate effects of this type of charcoal on sorption and desorption of pesticides in soil,synthetic charcoal from burning of red gum chips was mixed into soils at different rates,sorption and desorption behavior of diuron in the charcoal amended soils were determined by means of batch equilibrium and consecutive dilution techniques,respectively.For comparison,sorption and desorption of diuron in three natural soils with known contents of organic carbon and charcoalwere also measured.The sorption and desorption isotherms were fitted linearly with the Freundlich equation,and the ratio of sorption Freundlich exponent coefficient (N) and that of desorption (N_f) was used to indicate degree of sorption/desorption hystersis.Results of the sorption determination show the sorption capacity of the soil newly amended with charcoal increased with the rate of charcoal amended.The Freundlich sorption coefficient K increased from 4.08 to 500,while the other Freundlich coefficient (N) that shows the non linearity of sorption isotherm decreased from 0.83 to 0.16,when the content of charcoal in soil increased from 0% to 1.0%.The diuron sorption capacity of natural soils was related to the content of organic carbon,while the isotherm non-linearity was closely related with the relative content of organic carbon and charcoal.The higher the proportion of charcoal in total organic carbon,the higher the isotherm non-linearity.Results of the desorption experiment in soils newly amended with charcoal show that the desorption hystersis index H increased rapidly in value from 1.14 to 14.92 when the content of charcoal increased from 0% to 1.0% in the soil,and H values of natural soils SS7,SS8 and SS6 were 2.49,1.61 and 1.42,respectively,when the content of charcoal was 2.145%,0.819%,and<0.07%,respectively.The results indicated that the hysteresis effect of charcoal on desorption of diuron seemed to be closely correlated with the content of charcoal in the soils.